Testing system for automatic telephone switches



June 30, 1925. 1,543,900

A. S. BERTELS TESTING SYS'I'BI FOR AUTOMATIC TELEPHONE SWITCHES Filed 5 Sheets-Sheet 1 I Wye/flan Ame/d .S Ber/e/s. y

June 30, 1925.

A. s. BERTELS TESTING SYSTEM FOR AUTOMATIC TELEPHONE SWITCHES Filed July 23. 1923 5 Sheets-Sheet Mum/0r.- Ar/m/d J1 Berle/s.

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5 Sheets-Sheet 3 A. S. BERTELS Filed July 23, 1921.

TESTING SYSTEM FOR AUTOMATIC TELEPHONE SWITCHES June 30. 1925.

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June 30, 1925.

A. S. BERTELS TESTING SYSTEM FOR AUTOMATIC TELEPHONE SWITCHES Filed July 23. 1923 5 Sheets-Sheet 4 lawn/art. Ame/dd Ber/e/s.

June 30, 1925. 1,543,900

A. s. BERTELS TESTING SYSTEM FOR AUTOMATIC TELEPHONE SWITCHES Filed July 23, 1925 5 Sheets-Sheet 5 .270 )3? J74 if, I7 17/ .126 A '8' lo lo m ant 4.

Patented June 30, 1925.

UITED STATES PATENT OFFICE.

ARNOLD S. BERTELS, OI? TENAFLY, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TESTING SYSTEM FOR AUTOMATIC TELEPHONE SVJITCHES.

Application filed July 23,

To a?! :ctmm it may ('OHliti'i't.

lie it known that l. insombi. Bantams. a citizen of the i nited St ates of America, residing at l euatly. in the county of Bergen, State of New Jersey. have invented certain new and useful improvements in 'lestiug Systems for Automatic Telephone Switches. of which the following is a full, clear, concise. and exact description.

This invention relates to a telephone exchange system and more particularly to a tiriillg system for use in a machine switching system for testing selector switch units:

it an object of this invention to pro ide an improved testing system.

The i-"'\\iicliing units of an automaiicaiiy operated telephone exchange are made up of control ap iaratust relays and auxiliary circizit's to control its automatic progres on and further control other switching units and the line. large nutnhcr of such switching units are required in a system of this kind, any one of which may he arbitrarily selected. when idle. to complete a 3.5 -tertice connection. Thus, it is apparent that a switching unit giving inefficient service is not immediately noticed. Since the a p ratus of a switching unit requires adnctn's within limited variation it is im- 3 portaut that these units he regularly tested t" determine their ability to render efficient st rvice. in order to reduce the cost of such maintenance. it is desirable to use a testing system requiring a limited amount of manual operation.

.1 't'eaturc of this invention is in the use :1 common testing device.

A further feature of this invention is in the use of a common testing device to he i h the automatic switch under test.

further feature of this invention is in the provision of a common auxiliary testing c." or devices used in conjunction with a in "sting device.

further feature of this invention rclatcs to the use of an auxiliary testing dee seized under the control of a main testing device.

'ihe selector switch disclosed in this app ication is designed to associate itself with a line and to automatically connect continuous ringing potential to the line conductor "mm as the line is found to be idle. In operation. which is termed immediate ing" the ringing potential is connected 1923. Serial No. 653,125.

to the line for a predetermined period of time. Following the application of immediate ringing an interrupter is automatically connected to the line through which ringing potential is intermittently connected to in termitteutly ring the hell at the subscribers station. The ringing potential, either continuous or interrupted, is disconnected at the selector switch upon the removal of the receiver from the switchhook at the suhscl'iocl s station. A relay termed the "ringing relay in the selector switch opcrates to remove the ringing potential upon the elevation of the switchhook.

It is; therefore an additional object to test. s ile .witch units provided with ringing equipment.

he fullOWltl" features are incident to the attainment of this additional object.

feature of this invention is in the provision of a primary testing device. equipped with keys. to function as the register of a sender. in combination with a progression switch. to automatically control the connection of an incoming selector switch to one of a plurality of secondary testing devices The primary testing device remains positioned in such manner as to receive a signal upon the satisfactory completion of tests by the secondarv testing device.

A further feature of the invention is the provision of means for testing the adjustments of the ringing apparatus of a selector switch 'ith an automatically progressive testing device cont rolled by the automatically operating ringing apparatus of said selector switch.

A further feature of the invention relates to the automatic starting of the testing device from application of ringing potential and ringing ground by the selector switch.

A further feature of the invention relates to the response of the testing device to the application of immediate ringing potential by the selector switch and means for determining that immediate ringing and not interrupted ringing potential is first connected to the line conductors.

A further feature of the invention relates to the provision of means for properly recognizing the interrupted ringing potential during the tests of that feature.

A further feature of the invention resides in the provision of means for SYtttflliOlllZ- ing the progressive movement of the automatic testing device with the automatic application of ringing potential.

A further feature of the invention resides in the provision of means for making a plurality of false operation tests to determine whether the ringing relay in the selector switch will operate falsely preceding the removal of the receiver from the switchhook. plurality of tests are made so that one or more of these tests may be obtained at. a time when the ringing current wave is of maximum strength.

A further feature of the invention resides in automatic means for applying an operate test to the ringing relay in such manner that sluggish operation of said relay is detected.

A further feature of the invention relates to the provision of means for determining the success of the operating test of the ringing relay.

A further feature of the invention relates to means, at the termination of the selector switch ringing apparatus tests. to test the adjustment of the selector switch supervisory relay and means included in this test to operate a signal to indicate to a test-man that the apparatus in the selector switch under test is in correct adjustment.

These and other features of the invention will be apparent. from the following description taken in connection with the accompanying drawings.

lVhile the invention has been disclosed particularly adapted for testing switches of the panel type it will be apparent. however, from the following description that the invention has a wider utility and that by slight modilicatitm it could be adapted for testing other types of selector switches.

Figs. 1 and 2 show a testing and controlling circuit for directing the incoming selector switch and the final selector switch to an automatic testing device that is per manently connected to the multiple terminals of the multiple frame.

Fig. 2) shows the incoming selector switch to be tested.

Fig. 4 shows a final selector switch used to connect the incoming selector switch to the testing device. Fig. 5.

Fig. 5 shows the automatic testing device to which the incoming selector is connected for test. This testing device is connected to terminals in the final frame in place of lilies extending to subscribers stations.

Description of apparatus. The key set shown in Fig. l is made up of mechanically locking keys. The switch shown in Fig. 2 is of a well known step-by-step type.

The automatic selector switch shown in Figs. 3 and 4- are of the well known power driven type in which a plurality of sets of brushes are mounted on a vertical br'ush shaft arranged to be selectively tripped into engagement with an individual sequence of banks. The brush shafts are propelled in a vertical direction by means of constantly rotating power drums. In general construction and operation these switches are both of the same character as the one shown and described in detail in Patent No. 1,123,696 issued January 5,1913, to Edward B. (raft and John N. Reynolds. More specifically, the incoming selector shown in Fig. 3 and the final selector shown in Fig. 4 are described in Patent No. 1,395,977 issued November 1, 1921, to Franklin A. Stearm and Frederick J. Scudder.

The sequence switch shown in Fig. 5 is of the same general type as used in Figs. 3 and 4.

General clescriptzion.'llie test-man before preceding with a test of an incoming selector inserts plug 234 into jack 304 and plug 232 into jack 231. Certain of keys 130 to 169 are then actuated to register the line number to which the incoming selector switch is directed. A start key Q-ltl is then actuated by the test-man and from this point the operation is automatic until such time as trouble is encountered in the incoming selector switch or a signal is received by the test-man that an incoming selector switch has been tested and its apparatus found to be in correct adjustment.

Upon the actuation of the start key a progressively operated switch is actuated and in its progressive movement establishes circuits for directing the incoming selector switch to a particular final selector switch and the final selector switch is directed to an automatic testing device connected to certain final multiple terminals.

The incoming selector switch performs its functions the same as when it is connected to a line extending to a subscribers station. The ringing potential is thus connected to the testing circuit and is used as an automatic starting means to actuate the apparatus of the testing device, Fig. 5.

Various tests are now made of the ringing apparatus in the incoming selector switch, Fig. 3, to determine the accuracy of its adjustments. These tests are made throughout the progressive operation of the testing device until the ringing relay 314 is caused to operate thus rotating the incoming selector sequence switch into talking position. Following the operating test of the ringing relay 314, the testing device progresses to a position of its switch for test ing the supervisory relay of the incoming selector switch. The test applied to the supervisory relay 312 causes it to intermittently operate and release. thus connecting ground through its armatures and contact to the winding of a relay in the testing control circuit, Fig. 2. The intermittent operation of the relay in Fig. 2 establishes a cirion lit") cuit for flashing a lamp to indicate to the test-man that the test of the incoming selector switch is completed and its apparatus is in proper adjustment.

Having now described in a general way the apparatus employed in conducting tests and the manner in which it is to be used, it is thought that the invention will be better understood by a consideration of the specific manner in which it functions.

Detailed 1Zesm-ipfion.lt will be remembered from the general description that the test-man will first insert plug 232 into jack. 231 and plug 231 into jack 301 of the particular incoming selc; tor to le 5 He Will then consult his chart and depucs; the proper keys shown in Fig. 1 to control the incoming and final se ector switches to lect the line connected to the testing device shown in Fig. 5. Assuming that the te tin device is connected to line. 3190, keys 13:1, 141, 159 and 160 will be actuated. The actuation of the above-designated keys will as sociate certain of the counting relays with the terminals of terminal are 250, the functioning of which will be described hereinafter.

Key 2-10 is now actuated by the test-man to start the automatic progression of switch 200. The actuation of key 210 establishes a circuit for operating relay 213 which may be traced from grounded battery through the Winding of relay 213, contacts of key 210, right outer normal contact and armature of relay 212, terminal 1 of terminal are 250 to ground through brush 204. if the incoming selector switch, Fig. 3, is made busy from seizure by another selector switch, a circuit will be established for operating relay 210. This circuit may be traced from ground connected to the sleeve of jack Sill. sleeve of plug 234, sleeve conductor of patching cord 233, sleeve of plug 232, sleeve of jack 231. brush 205, terminal 1 of termi nal are 254, right normal armature and contact of relay 217, winding of relay 212 to battery. Relay 212 in attracting its right armature establishes a circuit for lighting lamp 228 to indicate the busy condition to the test-man. The circuit for lighting lamp 228 may be traced from ground through brush 204, terminal 1 of terminal are 253. right armature and contact of relay 212, lamp 228, resistance 223 to grounded battery. The circuit for actuating relay 213 upon the operation of key 210 is also opened at the right armature of relay 212. The operation of relay 212 prevents the procedure of test of a selector switch that busy. Assuming that the incoming selector switch. Fig. 3, is idle. relay 213 is operated through the circuit established and traced upon the operation of key 210.

The relay 213, in attracting its left and right armature, establishes a locking circuit for itself and an operating circuit for relay 217 which is effective upon the release of key 240. This circuit may be traced from grounded battery through the winding and left armature and contact of relay 213, winding of relay 217, right contact and armature of relay 213, left normal armature and contact of relay 211 to ground through contact and arn'iaturc of relay 11. Relay 217 in attracting its left armature establishes a circuit for actuating switch magnet 200 which may be traced from grounded battery through the winding and contact of switch magnet 200, brush 203, terminal 1 of terminal arc 252, armature and contact. of relay 217 to ground through right contact and armature of relay 220. The switch is thus rotated from terminal 1 to terminal lira-sh -1 in contact with terminal 2 to al 21 of terminal are 2433 establishes a awa t tor :u-tnating relay 221. This may be traced from grounded battery through winding of relay 221. terminals 2 to 21 of terminal are 2521, brush 204- to ground. The circuits established by relay 221 in attracting its armaturcs connect the incoming selen tor to the testing control circuit. These leads are m-mally held open to prevent connection of the testing control circuit to a busy incoming selector switch.

llrush 20:5 in contact with terminal 2 of terminal arc 252 establishes a circuit for energizing switch magnet 200 which may be traced from grounded battery through the winding and contacts of switch magnet 2t)0 brush 203. terminal 2 of terminal arc to ground, thus rotating the switch to terminal 3.

llrush 202 in contact with terminal 1, of terminal arc 2131 establishes a circuit for operating relay it). This may be traced from grounded battery through the wind- 'ng of relay 1U. terminal arc brush 202 to ground. The actuation of relay 1U connects grouiulcd battery through its tive right arniatures and contact to the windings of counting relays (3 to S) and in attracting its left a'uaturc c tabliuhcs a circuit for operating re y 220. This may be traced from grounded battery through the ar mature and contact of relay ltl. winding) of relay 22o to ground. ltclay 22a in attracting its armature establishes a circuit for actuating switch magnet 200. This may be traced from grounded battery through the winding and contacts of switch magnet 2W) brush 2021. terminal 3 of terminal are 252 to ground through contact and armature of relay 221'). thus rotating the twitch from terminal 3, to terminal l.

ith the switch brushes connected to term nal 11- the fundamental circuit for incoming brush selection is established.

The fundamental circuit may be traced from grounded battery through the right winding of relay 311, Fig. 3 upper contacts of sequence switch spring 321, resistance 315, upper contact of sequence switch spring 324, tip of jack 304, tip of plug 23-1, tip conductor of patching cord 233, tip t plug 232, tip 0t jack 23, outer right contact and an mature of relay 221, brush 200. t-er ninal 4- of terminal arc lett wimling ot relay 21 1i. winding of relay 215, contact and armature of counting relay 0, inner lett normal contact and armature of relay :2l2, inner lel't armature and contact o't relay 221, ring of jack 1331, ring of plug 232. ring conductor of patching cord 23; ring ol' plug 234-, ring of jack Slit, lower contact ot' sequence switch spring 222?. resistance $316 to ground through lower contact of sequence switch spring 335. Relays 311 and 215 are operated in this cir cuit. Relay 2i howeven does not operate at this time since it is polarized in the opposing direction to the current flow.

Pelay fill in attracting the let! outer armature establishes a circuit tor energizing sequence switch magnet Illa). This circuit may be traced from groui l battery through winding of magnet 3(a), lower contact o't sequence switch spring 32h. let't outer spring and armature ot relay ill I, to ground to lowercontact ofsequenceswitch spring I322. The sequence switch is thus rotated trom position 1 to position 2 where a holding circuit This may be is established for relay Sill.

raced from griiiunded battery through the right winding ot relay 311. right upper and lower (ontacts of sequence switch spring IlLl, right contact and armature of relay 2111, left upper and lower contacts of sequence switch spring 33d resistance lllfi, upper contacts o t sequence switch spring 324, tip spring of jack Sol, tip of plug 231, tip conductor of patching cord 2323. tip ot' plug 232, iip spring of jack 5231, left outer contact and armature of relay 122i. brush G, terminal l of terminal are 355, lel t. winding of relay LUX winding of stepping relay E2141 armature and contact ol counting relay l), left inner normal contact and armature ot relay 212, lct't inner armature and contact of relay 221, ring spring of jack Bill, ring of plug .332, ring conductor patching cord 23?), ring 0t plug LIll. ring spring o't jacl; Sol. lower contact ol sequence switch spring flail resistance 316 to ground through lower rontact of sequence switch spring 335.

In srqucnce switch position a circuit is also established tor energizing lip-drive magnet 302. This may be traced from grounded battery through the winding of lip-drive magnet 302, left upper contact of sequence switch spring Sill. le'lt outer contact and aru'iature of relay 311 to ground through lower contact of sequence switch spring 322. The selector switch elevator is now driven upward in the manner well known in the art, and in its upward move ment brush 341 is intern'iittently brought into contact with the conducting portion o't comn'iutator segment 34st. Thus a shunt circuit is established to cause the intermittent deenergization of stepping relay 215. This shunt circuit may be traced tron: ground through the lower contact of sequence switch spring 333, brush I-lll, commutator Sill. right lower contact ot sequence switch spring 336 to a junction point in the ci1= cuit established for operating relays 311 and 215. The shunt will not cause the release ot' relay I ll but will cause the release of relay 215.

The initial operation of relay 2t? over the "undanu-ntal circuit establishes a circuit tor operating counting relay 1. This may be traced l'rom ground through the armature and contact of relay Qli'a brush Q0], tern'iinal t of terminal are left contacts of hey 123i) winding o't counting relay .1, lit'th right contact and armature of relay ll) to gzroiuuled battery. The operation of counting relay 1 establishes a locking circuit tor itselt' and an operating circuit for counting relay 1' which is efl ective upon the lirst release of stepping relay .215. This circuit may be traced from ground through the armature and contact of counting relay 0 windings of counting relays O and l) to grounded buttery through filth right con tact and armature of relay 10.

The upward movement 01 the incoming selector switch elevator causes brushes till to more from the conducting portion of commutator segment 3-H to an insulated portion of this segment which will remove the shunt from stepping relay 2]?) and cause its reoperation over the original circuit traced to battery through relay 311. This operation of relay 215 will establish a circuit for operating the counting relay 0 which may be traced from ground through the armature and contact of relay 215, brush E201, terminal l of terminal are 250, left, contacts 01 key 133, armature and contact of counting relay 1, winding of counting relay 0, fifth right contact and armature of relay 10 to grounded battery. The upward movement of the incoming selector switch elevator will again establish the shunt circuit causing the release ot step-- ping relay 215. Upon the release of relay 215 the circuit established by the operation of counting relay 0 is effective for operating counting relay 0 and relay 1]. This may be traced from ground through armature and contact of counting relay 0, over a divided path through the windings of counting relay 0 and a relay 11 in multiple, thence through the winding of counting relay O fifth right contact and armature of relay 10 to grounded battery.

The operation of counting relay 0 opens ill) the fundmental circuit to cause the release of relay 311 which is effective as soon as brush 341 is moved to the insulated portion of commutator segment 344 next above the conducting segment that caused the second release of stepping relay 215. The release of relay 311 arrests the upward movement of the incoming selector switch elevator and establishes an actuating circuit for sequence switch magnet 300 which may be traced from grounded battery through the winding of sequence switch magnet 300, left upper contact of sequence switch spring 328 to ground through the left inner armature and contact of relay 311, rotating the sequence switch from position 2 to position 3.

Relay 11 in attracting its armature opens the holding circuit for relays 218 and 21. which release. and also establishes a circuit for actuating switch magnet 200. This actuating circuit may be traced from grounded battery through the winding and contacts of switch, magnet 200, brush 203, terminal 4 of terminal are 252 to ground through contact and armature of relay 11. Thus the switch is rotated from terminal 1 to terminal 5. The actuating circuit for relay 10 is now open, causing its release. The release of relay 10 causes the release of counting relays and relay 220 held in an operated position through its contacts. The release of relay 220 establishes an energizing circuit for switch magnet 200 which may be traced from grounded battery through. the winding and contacts of switch magnet 200, brush 203, terminal, 5 of terminal arc 252 to ground through contact and armature of relay 220. The switch is thus rotated from terminal 5 to terminal 6.

Brush 202 in contact with terminal 6 of terminal are 251 establishes an actuating circuit for relay 10. This may be traced from grounded battery through the winding of relay 10, terminal 6 of terminal are 251. brush 202'to ground. Relay 10 in attracting its right armatures establishes a source of grounded battery for operating the counting relays and in attracting its left armature. establishes an actuating circuit for relay 220. The actuating circuit for relay 220 may be traced from grounded battery through the left armature and contact of relay 10. winding of relay 220 to ground. The operation of relay 220 establishes a circuit for actuating switch magnet 200 which may be traced from grounded battery through the winding and contacts of switch magnet 200. brush 203, terminal (3 of terminal arc 252, contact and armature of relay 220 to ground. The switch is thus rotated to terminal 7 where the fundamental circuit is again established for incoming group selection.

The fundamental circuit is the same as previously traced with the exception that position 3 of the sequence switch, Fig. 3,

and terminal I of terminal arc 235 are used. Again relays 311 and 215 are operated upon the establisluncnt of the fundamental circuit. The operation of relay 311 establishes an actuating circuit for sequence switch magnet 300 which may be traced from grounded battery through the winding of sequence switch magnet 300, lower contact of sequence switch spring 2328. outer left contact and armature of relay 311 to ground through lowcr contact of sequence switch spring T22, rotating the sequence switch from position 3 to position 4. The holding circuit for relay 311 is again established upon the movement of the sequence switch from position 3 to position 4 and isthc same as previously traced. A circuit is established in sequence switch positions 3 and 4- for trip magnet 303, which may be traced from grounded battery through winding of trip magnet 303. right upper and lower contacts of sequence switch 333 to ground. The encrgization of the trip magnet causes brushes 350. 351 and to be brought into engagement with the bank terminals in the well known manner of such operation. A circuit is now established for up-drive l'nagnet 302 which may be traced from grounded battery through winding of magnet 302. right upper contact of sequence switch spring 331. left outer contact and armature of relay 311 to ground through lower contact of sequence switch spring 322. The incoming selector switch elevator and commutator brushes are now driven in an upward movement thus causing brush $3 12 to engage the conducting portion of connnutator 345 to establish a shunt for deenergizing stepping rclay 215. This shunt path may be traced from ground through lower contact of sequence switch spring 333, brush 342. conducting portion of commutator 34 1-. right upper contact of sequence switch spring 336 to a point of junction in the fundamental circuit where an effective shunt is placed around relay The initial operation of relay 21.") upon the establislnnent of the fundamental circuit establishes a circuit for operating counting relay 2. This may be traced from ground through the armature and contact of relay 215. brush 201. terminal 7 of terminal are 250. right contacts of key 133. left outer contacts of key 141. right normal contact and armature of counting relay 2. winding of counting relay 3. fourth right. contact and armature of relay 10 to grounded battery. The operation of counting relay 2 establishes a holding circuit for itself and an operating circuit for relay L" which is effective upon the release of relay 21 The release of relay 215. as described. is effective when brush 312 engages the conducting portion of commutator 345.

As the incoming selector switch elevator is driven in an upward movement, brush 2342 is intermittently engaged with non-conducting and conducting portions of conunutator segment 345 thus causing the intermittent energization and deenergization of stepping relay 215. Counting relays 1, 1, 0, O, and 11 are thus operated in the well known manner of operating counting relays.

The operation of counting relay 0 opens the fundamental circuit to release relay 311 when brush 342 arrives at the non-conducting portion of commutator segment 345, next above the conducting portion causing the release of relay 21.3 and the operation of counting relay 0'. The release of relay 311 arrests the upward movement of the incoming selector switch elevator and establishes an energizing circuit for sequence switch magnet 300. The energizing circuit may be traced from grounded battery through the winding of magnet 300. left upper contact of sequence switch spring 323 to ground through left inner armature and contact of relay 331. The sequence switch is thus moved from position 4 to position :1.

In sequence switch position 3 a circuit is again established for actuating relay 311. This may be traced from grounded battery through the left winding of relay 311. right upper and lower contacts of sequence switch spring 327 to ground. The operation of relay 311 establishes a circuit for energizing sequence switch magnet 300 which may be traced from grounded battery through the winding of magnet 300. lower contact of se quence switch spring 323. left outer c nta t and armature of relay 311 to ground through lower contact of sequence swit h spring 322. The sequence switch thus rotated from position 5 to position 6.

ln position 0 the incoi'ning selector switch seeking an idle trunk to a final selector circuit. A busy final selector circuit is characterized by ground impressed on terniinal 353. ,Assuming that an idle final selector switch has been immediately encountered relay 311 is released.

Since the trunlr hunting feature of this incoming selector switch is described in detail in previously referred to latcnt 1.35).),- tlTi'. it will be. omitted from this description.

The releasing of relay 311 connects a busy ground to terminal 353 to prevent other incoming selectors from stopping on the same terminal. This path may be traced from ground through the right upper contact of sequence switch spring 329, right normal contact and armature of relay 311, right upper and lower contacts of sequence switch spring 330, brush 350 to terminal 353. The release of relay 311 also establishes an actuating circuit for sequence switch magnet 300 which may be traced from grounded battery through winding of magnet 300 left upper contact of sequence switch spring 323 to ground through left inner armature and contact of relay 311. The sequence switch is thus rotated from position 6 into position 7.

In sequence switch position 7, a circuit is established for operating relay 311, which may be traced from grounded battery through the left Winding of relay 311, right upper and lower contacts of sequence switch spring 327 to ground. The operation of relay 311 establishes an energizing circuit for sequence switch magnet 300 which may be traced from grounded battery through the winding of magnet 300, lower contact of sequence switch spring 328, left upper contact and armature of relay 311 to ground through lower contact of sequence switch spring 322. The sequence switch is thus ro tated from position 7 to position 8 where it will remain until the final selector switch has completed units selection. In position 8 a circuit is established to hold relay 311. in an operated position. This circuit may be traced from grounded battery through the right winding of relay 311, right upper and lower contacts of sequence switch spring 321, right contact and armature of relay 311, right lower contact of sequence switch spring 321. brush 351, terminal 354, upper left and lower right contacts of sequence switch spring 421, resistance 4150, left lower contact of sequence switch spring 419 to ground.

It will be remembered that relay 11 was operated upon the completion of incoming selector switch group selection. The operation of this relay establishes a circuit for energizing switch magnet 200. Thismay be traced from ground through the armature and contact. of relay 11. terminal 7 of terminal are 252. brush 203. contacts and winding of switch magnet 200 to grounded bat: tery. The switch is thus rotated from terminal 7 to terminal 8 and upon leaving ter minal 7 opens the energizing circuit for relay 10. The deenergization ofrelay 10 causes the deenergization of the counting relays and the release of relay 220. The release of re lay 220 establishes an energizing path for switch magnet 200 which may be traced from ground through the armature and con tact of relay 220, terminal 8 of terminal are 252, brush 203, contacts and winding of switch magnet 200 to grounded battery. The switch is thus rotated from terminal 8 to terminal 9 where a circuit is again established for operating relay 10 through terminal 9 of terminal are 251, brush 202 to ground. The operation of relay 10 estalr lishes an operating circuit for relay 220 as previously traced. The operation of relay 220 establishes an energizing circuit for switch magnet 200 which may be traced from ground through the armature and contact of relay 220, terminal 9 of terti a minal are 251, brush 203 to contacts and winding of switch magnet 200 to grounded battery. The switch is thus rotated from terminal 9 to terminal 10.

The fundamental is now extended to the final selector switch, Fig. 4. This fundamental circuit maybe traced from grounded batt ery through the left upper contact of sequence switch spring 416. right winding of relay 407. left lower contact of sequence switch spring 418, left lower contact of sequence switch spring 422, terminal 355, brush left upper contact of sequence switch spring 332, resistance 315, right upper contact of sequence switch spring 824. tip spring of jack 301, tip of plug 234, tip conductor of patching cord Q33, tip of plug 232, tip spring of jack 231, right outer contact and armature of relay 221. brush 206. terminal 10 of terminal arc 255. left winding of relay 214. winding of relay 215, contact and armature of counting relay ll. right inner normal contact and arn'iature of relay 212, left inner arniature and contact of relay 22].

ring spring of jack 231, ring of plug 232, ring conductor of patching cord 233. ring of plug 234, ring spring of jack 210}. right lower contact of sequence switch spring 32", resistance 316 to ground through right lower contact of sequence switch spring 335. Relay 4-07 and relay 2l5 operate upon the establishment of this circuit.

Relay 407 in attracting its left armature establishes a circuit for energizing relay 406. This circuit may be traced from grounded battery through the left winding of relay 406. left upper contact of sequence switch spring tti'. left contact and armature of relay to? to ground through left upper contact of sequence switch spring "llfl. The operation of relay 406 establishes a locking circuit for itself from grounded battery through its left winding, the normal arma ture and contact of relay 405, left contact and armature of relay 406. terminal 35-), brush 350. right lower and left upper contacts of sequence switch 360 to ground. He lay 106 in attracting its right armature establishes an energizing circuit for magnet too. This may be traced from ground through the right armature and contact of relay =ttlt3. lower contacts of sequence switch spring 1 l l, winding of sequence switch magnet 'ttltl to grounded battery. Thus the sequence switch is rotated from position 1 to position 2.

l'pon the moyemcnt of the sequence switch from position 1 to position 2 a holding circuit is established for relay 407 which may be traced from grounded battery through the left upper contact of sequence switch spring 416. right winding of relay ltli. lower contact of sequence switch spring 415, right contact and armature of relay 407, right lower contact of sequence switch spring ll l, left lower contact of sequence switch spring 432 and thence over he fundamental circuit to ground as preyiously traced.

In sequence .v-iitch position 2 a circuit is established for energizing up-drire magnet 402%. This may be traced from grounded battery through the wint'ling of magnet 44% rightuppcr contact of sequence switch spring 426. left contact and armature of relay to? to ground through left upper contact of sctptence switch spring 410. The final select r switch elcfator is now driyeu upward to make brush selection and brush till is brought into contact with commutator sce'ment ti' thus intermittently establishi a shunt for stepping relay 21.3. This shunt path may be traced from ground through the right upper contact of sequence swit h spring lif brush 1 31. commutator sgment i right upper contact of seqii nce s c spring 422 to the fund:\

. ntal circuit '2 in tial operation of relay 121.3 oyer the l ci cuit establishes an cncrgizfor counting relay 1. This cirt m y he tnccd from ground through the armature and contact of relay 215. 'nsh :34)! t tiitlP-Ell it) of terminal arc 25 h b .lt contact of lcey Ill. normal contacts of counting relay 1. winding of counting relay 1. fifth right ci'intact and armature of relay i to grounded batte y. The opera tion of counting relay l establishes a locl\'- ing circuit for itself and an operating circui for relay 1' which is etl'ectiye upon the ill? release of stepping relay 215 when the hunt is cstahlivhcil. Counting relays l t! and 11 will be operated in the well known manner of operating counting relays. The epcmtion of counting relay 0' opens the 't'unilalncutal circuit which will cause the release of relay hi7. wh n brush -liil moves upward to a ncirconducting portion of com mutator segment til-t.

The release of relay ttli arrests the up ward movement of the selector switch elevator and establishes an energizing circuit for sequence switch magnet ttltl. This cncrgizing circuit may be traced from grounded battery through the winding of magnet ttltl, right upper contact of sequence switch spring ll i. left normal contact and armature of relay 407 to ground through left upper contact of sequence switch spring till. The sequence switch is thus rotated from position to position 3.

The operation of counting relay ll est-ablishes an actuating circuit for switch magnet But) which may be traced from ground through the armature and contact of count ing relay 11. terminal 10 of terminal, arc brush 203, contacts and winding of switch magnet 200 to grounded battery thus ltltl rotating the switch from terminal 10 to ter minal 11. The stepping of brush 2.02 from terminal 10 to terminal 11 opens the energizing circuit or relay 10 which releases. The release of relay 10 deenergizes the counting relays that have been operated and also deenergizes relay 220. The deenergization of relay 7720 establishes a circuit 't'or energizing switch magnet 200 which may be traced from ground through the armature and contact of relay terminal 11 of terminal arc brush 203, contacts and winding oi" switch magnet 200 to groundet'l battery thus rotating the switch from terminal 11 to terminal 1?.

Brush 202 in contact with terminal 113 ot terminal are 251 establishes an actuating circuit for relay 10 the same as previously traced. Relay ht in attracting its right ari'naturcs connects grounded battery to the windings of the counting relays and in attr: cting its left armatnrcs e tablishes an obvious operating circuit tor relay The operation of relay 22h establishes an actuating circuit for switch magnet coo which may be traced from ground through the arn'iature and contact of re ay 212th term nal 12 of terminal are 252. brush 20 3, contacts and winding of switch magnet fitlt) to grounded battery thus rotating the switch from terminal 12 to terminal it; where the fundamental circuit is again established for tens selection ot the final selector switch.

It will be remen'ibered that the sequence switch of the tinal selector, Fig. is resting in position 3. 'lhcretorc, upon the closure of the fundamental a circuit is established tor (lptl'tlt lllfl relay to? and relay 215. This may be traced from grounded battery through left upper contact ot sequence switch spring 41th right winding of relry 407. let't lower contact of sequ'nce switch spring 419. lctt lower contact ot sequence switch spring "1:22 and thence over the fundamental through the winding of relay 5215 to ground at sequence switch spring 335 as previously traced. The operation of relay to? establishes an actuating circuit tor sequence switch magnet 400 which may be traced from grounded battery through the winding of sequence switch magnet 400. lower contact of sequence switch spring H3. lett contact and armature of relay 110T to ground through upper contact of sequence switch spring 410. The sequence switch is thus rotated "from position I, to position and in rotating to position i the holding circuit lor relay 407 is established as previmtsly traced.

tn sequence switch position 3 and "i an obvious circuit is established tor energizing the trip magnet 4.04 to cause he actuation of the tripping spindle in the well known manner. Brushes 437, 438 and 439 are now prepared to engage the bank terminals upon the subsequent upward movement of the selector switch elevator.

Upon the. forward movement of the sequence switch into position 1, a circuit is established for the high speed up-drivemagnet 403. This may be traced from grounded battery through the winding of magnet 403, right upper contacts of sequence switch spring 426, left contact and armature of relay 407 to ground through upper contact of sequence switch spring 410. The selector switch elevator is thus driven in an upward movement to bring brush 132 into engagc rnent with commutator segment 435. The engagement of this brush with the conducting portion of commutator segment 435 establishcs a shunt circuit ctl ective tor releasing stepping relay 215. This shunt path may be traced from ground through the left upper contact of sequence switch spring 419, brush 1532. conducting portion of commutator segment 435). right upper contact of sequence switch spring 418, left lower conta t of sequence switch spring 432 and thence over the fundamental circuit causing the release of relay 215.

The initial actuation of stepping relay 215 establishes a circuit tor operating counting relay 9 which may be traced from ground thrt h tln armature and contact of relay 215. brush 201, terminal 13 of terminal arc 35th right contacts of key 159, normal armature and contact of counting relay 9, wind ing o't' counting relay 9, first right contact of relay 10 to grounded battery. The operation of counting relay 9 establishes a holding circuit for itself and an operating cirsuit for counting relay 9 which is etl ective upon the first release of stepping relay 215. Upon the upward movement of the final selet-tor switch elevaton brush 432 is intermittently engaged with the conducting and non-conducting portions of commutator segment 435, intermittently ope ating and releasing stepping relay 215. The counting relays are energized from the intern'iittent energization and dcenergization ot stepping relay 215 in the well known manner of operating countying relays until all of the counting relays including counting relay 0 and relay 11 have been energized.

The operation of counting relay 0 opens the fundamental circuit to cause the release of relay 407 as soon as the shunt ground is removed at commutator 435. The release of relay .07 arrests the upward movement of the final selector switch elevator and establishes a circuit for energizing sequence switch magnet 4:00. This energizing circuit may be traced from grounded battery through the winding of magnet 400, right upper contact of sequence switch spring 413, left norn'ial contact and armature of relay 407 to ground through upper contact of sequence switch spring 410. The sequence loo LMWO

switch is thus rotated from position '4 to position 5 where it awaits further action of the control circuit.

The operation of counting relay 11 establishes a circuit for actuating switch magnet 200 which may be traced from ground through the armature and contact of counting relay 11, terminal 13 of terminal are 252, brush 203, contacts and Winding of switch magnet 200 to grounded battery. The switch is thus rotated from terminal 13 to terminal 14, opening the energizing circuit for relay 10. The release of relay 10 removes the operating battery from the counting relays, causing their release. The release of relay 10 also opens the energizing circuit for relay 220 causing its release. The release of relay 220 establishes a circuit for energizing switch magnet 200 which may be traced from ground to the armature and ontact of relay 220, terminal 14 of terminal arc 252, brush 203, contacts and winding of switch magnet 200 to grounded battery. The switch is thus rotated from terminal 14 to terminal 15 where the operating circuit for relay 10 is reestablished as previously traced. The operation of relay 10 connects grounded battery to the windings of the counting relay and establishes an obvious energizing circuit for relay 220. Relay 220 in attracting its armature establishes a circuit for energizing switch magnet 200 which may be traced from ground through the armature and contact of relay 220, terminal 15 of terminal are 252, brush 203, con

tacts and winding of switch magnet 200 to grounded battery. The switch is thus rotated. from terminal 15 to terminal 16 to reestablish the fundamental circuit for final units selection.

It will be remembered that the sequence switch in the final selector, Fig. 4, is standing in position 5. A circuit is now established for energizing relay 407 and relay 215 over the fundamental circuit to cause units selection to take place. This energizing circuit may be traced from grounded battery through the left upper contact of sequence switch spring 416, right winding of relay 407, left lower contact of sequence switch spring 418. left lower contact of sequence switch spring 422, and thence over the fundamental circuit through the winding of relay 215 to ground at sequence switch spring 335. as previously traced. Relay 407, in energizing. establishes an energizing circuit for sequence switch magnet 400 which may be traced from grounded battery through the winding of magnet 400, lower contact of sequence switch spring 413, left contact and armature of relay 407 to ground through upper contact of sequence switch spring 410. The sequence switch is thus rotated from position 5 to position 6 and in rotating to position 6 establishes a holding circuit for relay 407 as previously traced.

In sequence switch position 6 an energizing circuit is established for slow speed updrive magnet 402. This may be traced from grounded battery through the winding of magnet 402, lower contact of sequence switch spring, 417, left contact and armature of relay 407 to ground through upper contact of sequence switch spring 410. The final selector switch elevator is now driven upward causing the upward movement of brush 431 in contact with commutator segment 434. Since the final selector switch is directed to the first or zero terminals in a group of ten, the shunt path for deenergizing stepping relay 215 is immediately established to cause the energization of count ing relays 0 and 11. This shunt path may be traced from ground through the left upper contact of sequence switch spring 419, brush 431, conducting portion of commutator segment 434, right upper contact of sequence switch spring 422 to a junction joint in the fundamental circuit effective for maintaining relay 407 in operated position and releasing stepping relay 215.

The initial operation of relay 215 establishes the above mentioned energizing circuit for counting relay 0. This may be traced from ground through the armature and contact of relay 215, brush 201, terminal 16 of terminal are 250, left contacts of key 160, winding of counting relay 0, fifth right contact and armature of relay 10 to battel-y. The operation of counting relay 0 establishes a holding circuit for itself and an operating circuit for counting relays 0' and 11 which is effective upon the release of step ping relay 215.

The operation of counting relay 0 opens the fundamental circuit to cause the release of relay 407 which becomes effective as soon as brush 431 is elevated to a non-conducting portion of commutator segment 434. The release of relay 407 arrests the upward movement of the selector switch elevator and establishes an energizing circuit for the sequence switch magnet 400. This energiz ing circuit may be traced from grounded battery through the winding of magnet 400, right upper contact of sequence switch spring 413, left normal contact and armature of relay 407 to ground through upper contact of sequence switch spring'410. The sequence switch is thus rotated out of posi tion 6 and into position 9 under the control of the sequence switch magnet contact.

The operation of counting relay 11 establishes an energizing circuit for switch magnet 200' which may be traced from ground through the armature and contact of counting relay l1, terminal 16 of terminal arc 252, brush 203, contacts and winding of switch magnet 200 to grounded battery.

The switch is thus rotated from terminal 16 to terminal 17, opening the energizing circuit for relay 10. The deenergization of relay 10 opens the energizing circuit for the counting relays causing them to be released and also opens the energizing circuit for relay 220 causing its release. The deenergization of relay 220 establishes an energizing circuit for switch magnet 200 which may be traced from ground through the armature and contact of relay 220, terminal 17 of terminal'arc 252, brush 203, contacts and winding of switch magnet 200 to grounded battery. The switch is thus rotated from terminal 17 to terminal 18. Brush 206 in contact with terminal 18 of terminal are 255 establishes the fundamental circuit previously traced. The switch will now remain in position 18 to further control the incoming selector switch, Fig. 3, as will be described later.

It will be remembered that the release of relay 407 rotated the final selector sequence switch into position 9. In this position of the sequence switch a circuit is established for operating relay 407. This may be traced from grounded battery through the left upper contact of sequence switch spring 416, right winding of relay 407, lower right and upper left contacts of sequence switch spring 415 to ground through right contact and armature of relay 406. The operation of relay 407 establishes an energizing path for sequence switch magnet 400 which may be traced from grounded battery through the winding of magnet 400, lower contact of sequence switch spring 413, left contact and armature of relay 407 to ground through upper contact of sequence switch spring 410. The sequence switch is thus rotated out of position 9 and into position 12 under the control of the sequence switch magnet contact.

In position 12 of the final selector sequence switch, the line is tested to determine whether it is in a busy or idle condition. Since there are a number of testing devices the same as that shown in Fig. 5, connected to adjacent line terminals the P. B. X. hunting feature of the final selector switch is employed to connect the final selector switch to an idle one of these testing devices. Busy line terminals connected to a testing device are characterized by grounded battery connected to terminal 440 derived from a final selector switch the same as Fig. 4. This may be traced from grounded battery through the right upper contact of sequence switch spring 416, resistances 424 and 423, lower contacts of sequence switch spring 420, brush 437 to terminal 440. An idle line connected to a testing device is characterized by ground connected to terminal 440 through the winding of relay 505 and the upper contact of sequence switch spring 520.

Assuming that the first line connected to a testing device is busy a circuit is established for holding relay 407 actuated. This circuit may be traced from grounded battery in a circuit the same as that shown in Fig. 4, through right upper contact of sequence switch spring 416 resistances 424 and 423, lower contacts of sequence switch spring 420, brush 437, contact 440 to brush 437 in the final selector switch now being desc 'bed, through right lower and upper contac s of sequence switch 420, right armature and contact of relay 407, right upper contact of sequence switch spring 415, right winding of relay 407, left lower contact of sequence switch spring 418, left upper contact of sequence switch spring 422, winding of relay 405 to ground. Relay 405 does not receive suflicient current to operate in the circuit just traced since it is in multiple with the winding of relay 505 which is of low resistance.

With relay 407 held in an operated position to grounded battery in the busy connection, an energizing circuit for slow speed up-drive magnet 402 is established. This energizing circuit may be traced from grounded battery through the winding of magnet 402, lower contact of sequence switch spring 417, left contact and armature of relay 407 to ground through the upper contact of sequence switch spring 410. The final selector switch elevator is now driven in an upward movement until brush 437 is brought into engagement with a line connected to an idle testing device characterized by ground connected to terminal 440. The holding circuit for relay 407 is thus opened to cause its release. Relay 407 in releasing opens the energizing circuit for updrive magnet 402 thus arresting the upward movement of the final selector switch elevator. The release of relay 407 also establishes an energizing circuit for sequence switch magnet 400 which may be traced from grounded battery through the winding of magnet 400, right upper contact of sequence switch spring 413, left normal contact and armature of relay 407, left lower contact of sequence switch spring 410 to ground through right contact and armature of relay 406. The sequence switch is thus rotated from position 12 to position 13.

In sequence switch position 13 a circuit is established for sequence switch magnet 400 which may be traced from grounded battery through the winding of magnet 400, lower contacts of sequence switch spring 411 to ground through right contact and armature of relay 406 thus rotating the sequence switch to position 14 where a circuit is again established for actuating sequence switch magnet 400. This may be traced from grounded battery through winding of magnet 400, right upper contact of sequence switch spring 413, left normal contact and armature of relay 407 to ground through upper contact of sequence switch spring 410. The sequence switch is thus rotated from position 14 to position 15 where it will remain until the incoming selector, Fig. 3, has been tested.

It will be remembered that the incoming selector switch remained in position 8 during the control of the final selector switch. During this time relay 311 remained actuated over a path traced from grounded battery through right Winding of relay 311, right upper and lower contacts of sequence switch spring 321, right contact and armature of relay 311, right lower contact of sequence switch spring 331, brush 351, terminal 354, upper left and lower right contacts of sequence switch spring 421, resistance 450, left lower contact of sequence switch spring 419 to ground. This holding circuit for relay 311 was opened when the final selector sequence switch rotated from position 8 to 9 as previously described and at this time relay 311 is deenergized to establish an energizing circuit for sequence switch magnet 300. This energizing circuit may be traced from grounded battery through the winding of magnet 300, left upper contact of sequence switch spring 328, left inner armature and contact of relay 311 to ground. The incoming selector sequence switch 300 is thus rotated from position 3 to position 9.

In position 9 of the incoming selector sequence switch battery and ground is reversed with relation to the fundamental circuit. This is done to signal the controlling circuit, Fig. 2, when final selections have been completed and relay 311 released. This fundamental circuit may be traced from grounded battery through the right winding of relay 311. lower contacts of sequence switch spring 325, resistance 316, lower contact of sequence switch spring 323, ring spring of jack 304, ring of plug 234, ring conductor of patching cord 233, ring of plug 232, ring spring of jack 231, left inner contact and armature of relay 221, left inner normal armature and contact of relay 212, contact and armature of counting relay 0, winding of stepping relay 215, left winding of polarized relay 214, terminal 18 of terminal arc 255, brush 206, left outer armature and contact of relay 221, tip spring of jack 231, tip of plug 232, tip conductor of patching cord 233, tip of plug 234, tip spring of jack 304, upper contact of sequence switch spring 324, resistance 315. left lower and upper contacts of sequence switch spring 336, upper contacts of sequence switch spring 330 to ground. Relays 311, 215 and 214 are operated in this circuit.

The operation of relay 214 establishes an actuating path for relay 216 and a locking circuit for itself which may be traced from ground through brush 204, terminal are 253, contact and armature of relay 214, through the windings of relays 214 and 216 in multiple to grounded battery. Relay 216 upon attracting its right outer armature establishes a circuit for lamp 230 to indicate the progress of the test to the test man. The circuit for lighting lamp 230 may be traced from grounded battery through resistances 225, lamp 230, right outer contact and armature of relay 216, terminal 18 of terminal arc 251, brush 202 to ground. Relay 216 in attracting its left armature establishes a circuit for operating counting relay 0. This circuit may be traced from ground through the armature and contact of stepping relay 215, brush 201, terminal 18 of terminal are 250, left contact and armature of relay 216, winding of counting relay 0, fifth right contact and armature of relay 10 to grounded battery. It will be noted that relay 10 is actuated from ground at brush 202. The operation of counting relay 0 establishes a locking circuit for itself and an operating circuit for counting relays 0 and 11 which is effective upon the release of relay 215. Relay 215 while operated maintains a shunt ground around the windings of counting relays 0 and 11. Relay 215 is released upon further rotation of the incoming selector sequence switch as will be described.

The operation of relay 311, as described upon the closure of the fundamental, establishes a circuit for actuating relay 310. This may be traced from grounded battery through the winding of relay 310, right upper contact of sequence switch spring 326, right contact and armature of relay 311, upper contacts of sequence switch spring 326, right contact and armature of relay 311, upper contacts of sequence switch spring 330 to ground. The operation of relay 310 establishes an actuating circuit for sequence switch magnet 300 which may be traced from grounded battery through the winding of magnet 300, contact and armature of relay 310, left lower and upper contacts of sequence switch spring 330 to ground. The sequence switch is thus rotated from position 9 to position 10 thereby opening the fundamental circuit to cause the release of relay 215. Counting relays 0 and 11 are now operated from ground through the armature and control of counting relay 0, windings of counting relays 0 and 11, to grounded battery through the fifth right contact and armature of relay 10. The operation of counting relay 0 causes the fundamental circuit to remain open until the control circuit, Figs. 1 and 2, can adjust itself to further control the incoming selector, Fig. 3. The operation of counting relay 11 establishes a-circuit for energizing switch magnet 200 which may be traced from ground through the armature and contact of counting relay 11, terminal 1.8 of terminal arc 252, brush 203, contacts and winding of switch magnet 200 to grounded battery. The switch is thus rotated from terminal 18 to terminal. 19 causing the release of relay 10, relay 220 and the counting relays as previously described.

Brush 206 in contact with terminal 19 of terminal are 255 establishes what is known as trunk closure with relation to the incoming selector switch, Fig. 3. This simulates the connection of the incoming selector switch to a calling subscriber preceding the ringing of the wanted subscribers station. The circuit establishing trunk closure may be traced from grounded battery through the right winding of relay 311, upper contacts of sequence switch spring 321, resistance 315, upper contact of sequence switch spring 324, tip spring of jack 304, tip of plug 234. tip conductor of patching cord 233, tip of plug 232, tip spring of jack 231, outer contact and armature of relay 221, brush 206, terminal 19 of terminal are 255 resistance 226, polarized relay 218, left inner normal contact and armature of relay 212, inner armature and contact of relay 221, ring spring of jack 231, ring of plug 232, ring conductor of patching cord 233, ring of plug 234, ring of spring 304, lower contact of sequence switch spring 323, resistance 316 to ground through lower contact of sequence spring 335. Since relay 218 is polarized in the opposing direction to the current flow in the circuitpath just traced it will not operate. Relay 311, however, operates to establish an energizing path for sequence switch magnet 300 to rotate the sequence switch into the position for connecting, what is known as, immediate ringing potential to the line. The circuit for actuating relay 310 is reestablished by the operation of relay 311 and the circuit for energizing sequence switch magnet 300 may be traced from grounded battery through the winding of magnet 300, contact and armature of relay 310, left lower and upper contacts of sequence switch spring 330 to ground. The sequence switch is thus rotated from position 10 to position 11.

In sequence switch position 11, relay 311 is held in an operated position over the circuit traced from grounded battery through the left winding of relay 311, armature and contact of relay 314, left upper contact of sequence switch spring 334, left outer contact and armature of relay 311,

upper contact of sequence switch spring 322, sleeve of jack 304, sleeve of plug 234, sleeve conductor of patching cord 233, sleeve of plug 232, sleeve of jack 231, brush 205, terminal 19 of terminal are 254, winding of relay 219, coil 257, to ground through terminal are 253 and brush 204.

Coil 257 is of low resistance and coil 258 is of high resistance thus forming a potentiometer so that relay 219 will operate from either grounded battery or ground connected to the sleeve of jack 304. Relay 219 therefore, operates upon the rotation of switch 200 to terminal 19 and remains operated during the remainder of time that the incoming selector switch, Fig. 3, is being tested. The operation of relay 219 establishes a circuit for energizing the winding of relay 210. This circuit is obvious and need not be traced. The operation of relay 210establishes a circuit for lighting lamp 227 from grounded battery through resistance 222, right outer contact and armature of relay 210, lamp 227, contact and armature of relay 218 to ground through left armature and contact of relay 210. The utility of this lamp will be described later.

Preceding position 11 of the incoming selector sequence switch, Fig. 3, the said incoming selector switch has been controlled and tested by the testing device shown in Figs. 1 and 2. In position 11 and further positions of the sequence switch to be described later, the normal function of the incoming selector is to apply ringing potential to the line conductors to ring the bell at a subscribers station and remove said ringing potential immediately upon the removal of the receiver from the subscribers station switchhook. Fig. 5 is designed to automatically operate to simulate the subscribers station including the removal of the receiver from the switchhook.

The testing device shown in Fig. 5 is started in its operation by the application of ringing potential and ringing ground from the incoming selector and from that point it automatically applies test to the incoming selector apparatus. As the incoming selector progressively operates it must respond to these tests if its apparatus is in correct adjustment.

Ringing ground is applied to the tip conductor of the incoming selector, Fig. 3, at the right upper contact of sequence switch spring 332 establishing a circuit for operating relay 506. This may be traced from ringing ground through the right upper contact of sequence switch spring 332, brush 352, terminal 355, lower contacts of sequence switch spring 422, brush 439, terminal 442, conductor 502, left upper contact of sequence switch spring 529, left winding of relay 506 to grounded battery. The operation of relay 506 establishes a circuit for energizing sequence switch magnet 500 which may be traced from grounded battery through the winding of magnet 500, left upper contact of sequence switch spring 524 to ground through left contact and armature of relay 506. The sequence switch is thus rotated from position 1 to position 2 and from position 2 to position 3 under the control quence switch spring 526, winding of relay 509, right normal contact and armature of relay 510, lower contact of sequence switch spring 524, left contact armature of relay 506 to ground. The operation of relay 509 establishes a locking circuit for itself through its right inner contact and armature to ground, through the left inner contact and armature of relay 511. Relay 509 in operating does not establish any other effective circuit at this time. Upon the termination of the immediate ringing period relays 506 and 507 are released. The release of relay 506 establishes a circuit for operating relay 510. This may be traced frgm ground through the left normal contact and armature of relay 506, upper contact of sequence switch spring 525, left outer armature and contact of relay 509, winding of relay 510, contact of sequence switch spring 526 to grounded battery. Relay 510 in operating establishes a locking circuit for itself through its left inner contact and armature to ground through right contact and armature of relay 512. The operation of relay 510 does not establish any other efiective circuit at this time. I

The test of the immediate ringing has now been completed and the apparatus in the testing device, Fig. 5, is positioned to proceed with further tests. This indicates correct adjustment of the apparatus tested. The immediate ringing is used in the normal functioning of this type of incoming selector circuit to immediately ring the subscribers bell when the incoming selector and final selector are connected to a subscribers line. After a time interval this immediate ringing potential is replaced by ringing potential applied to the line through the commutator segment of an interrupter. The interrupted ringing current remains connected to the line conductors until such time as the receiver is removed from the switchhook or the calling party disconnects. A number of calls are established preceding the application of the interrupted ringing.

In position 13 of the incoming selector sequence switch, interrupted ringing potential and ringing ground is applied to the line, and a circuit is established for again operating relay 507 of the testing device positioned in sequence switch position 4. This path may be traced from ringing potential through conducting segments of interrupter 306, right lower contact of sequence switch spring 320, relay 314, lower contacts of sequence switch spring 321, right contact and armature of relay 311, right lower contact of sequence switch spring 331, brush 351, terminal 354, upper contacts of-sequence switch spring 421, brush 438, terminal 441. conductor 503, condenser 550, winding of relay 507 to ground through right upper contact of sequence switch spring 530. The

operation of relay*507 establishes a circuit for operating relay 506 which may be traced from ringing round through the right up-' groun ed battery through the contact of sequence switch spring 526, winding of relay 511, left outer normal contact and armature of relay 512, right contact and armature of relay 510, lower contact of sequence switch spring 524, to'grourid through left contact and armature of relay 506. It will be noted that the operation of relay 511 causes the release of relay 509. Relays 506 and 507 remain operated during the period of time that interrupter 306 is rotated with the conducting segment connected to the contact of sequence switch spring 320. At the end of this period of time, relays 506 and 507 release, establishing a circuit for rotating sequence switch 500 from position 4 to position'5. I

The foregoing operation and release of relays 506 and 507 is t'o prepare the testing circuit, Fig. 5, to move its sequence switch into testing position 5 with assurancethat the test-maybe made when the conducting segment of interrupter 306 is first connected to the contact of sequence switch spring 320. In this manner the full time period of ring ingis connected to testing device. As is well known in the art, sequence switch 300 may move into position 13 at a time when interrupter 306 has partly rotated over the conducting portion of-its segment with relation to the contact of sequence switch spring 320. v i

The circuit established for rotating sequence switch 500 into position 5 may be traced from grounded battery through the winding of magnet 500, lower contact of sequenceswitch spring 535,-left outer contact and-armature of relay511,-left outer normal contact and armature ofrelay 509, upper contact of sequence switch spring 525,1eft normal contact and. armature of relay 506 to ground. The sequence switch in rotating from position 4-to 5- opens the holding circuit for relays 510 and; 511 causing their release. i I

With sequence switch 500 in position 5, the testingdevice is prepared to make a test for prematureor false operation of the ringing relay 314, and since the time interval for movin sequence switch 500- from'position 4 to position 5 is of shorter duration than the time occupiedby interrupter 306for moving from one conducting segment to the next, this premature operation test will take place when said next conducting segment of interrupter 306 is connected to the contact of sequence switch spring 320. This premature operation test will also be known in this description as a premature tripping test.

Ringing potential from interrupter 306 now establishes a circuit for operating relay 507. This may be traced from ringing potential through the conducting portion of interrupter 306, left lower contact of sequence switch spring 320 and thence to conductor 508 of Fig. 5 as previously traced, thence through condenser 550, winding of relay 507, left upper contact of sequence switch spring 530, conductor 502 and thence to ringing ground at sequence switch spring 332 over the path previously traced. The operation of relay 507 establishes a circuit for operating relay 506 which may be traced from grounded battery through the left winding of relay 506, upper contact of sequence switch spring 527, contact and armature of relay 507 to ground through right upper contact of s uence switch spring 521. The operation of i elay 5-06 establishes a circuit for energizing sequence switch magnet 500 which may be traced from grounded battery through the windingof magnet 500, upper contact of sequence switch spring 524 to ground through left contact and armature of relay 506. The sequence switch is thus rotated from position 5 to position 6 and in rotating from position 5 to position 6 opens the circuit traced for operating relay 506. This relay, however, in position 6 is connected to interrupter 5'51and is opera'ted and released upon each rotation of this interrupter. Its operating path may be traced from grounded battery through the left winding of relay 506, left lower contact of sequence switch spring 534, conducting segment of interrupter 551 to ground through the right lower contact o-f sequence switch spring 528. Upon the first operation of relay 506 under the control of interrupter 551, a circuit is established for operating relay 509. This circuit may be traced from grounded battery through the contact of sequence switch spring 526, winding of relay 509, right normal contact and armature of relay 510, lower contact of sequence switch spring 524, to ground through left contact and armature of relay 506. Relay 509 tablishes a locking path for itself to ground at the right normal armature of relay 512. When interrupter 551 rotates to a nonconducting portion of the segment, relay 506 is released establishing a circuit ior energizing relay 510. This energizing circuit may be traced from grounded battery through the contact of sequence switch spring 526, winding of relay 510, left outer contact and armature of relay 509, upper contact of sequence switch spring 525 to ground through left normal contact and armature of relay 506. Relay 510 establishes an obvious locking circuit for itself which need not be traced and also in attracting its left outer armature establishes a circuit for the premature tripping test which is effective upon the subsequent op eration of relay 506. The second operation of relay 506 under the control of interrupter 551 establishes a circuit for making the premature trip test upon ringing relay 314. The circuit established for making this premature trip test is of such value in resistances that the test of the adjustment of relay 314 is more severe than is encountered in actual service. This circuit may be traced from ringing potential through the conducting segment of interrupter 306, right lower and upper contacts of sequence switch spring 320, winding of relay 314 and thence over the path previously traced to conductor 503 in Fig. 5, through resistances 560, 561, 562 and 563, lower contact of sequence switch spring 531, right normal contact and armature of relay 511, left outer armature and contact of relay 510, upper contact of sequence switch spring 533 and thence over conductor 502 to ringing ground at sequence switch spring 332 as previously traced.

During the period of time that relay 506 is held in an operated position for the premature trip test, a circuit is established for operating relay 511. This may be traced from grounded battery through the contact of sequence switch spring 526, winding of relay 511, left outer normal contact and armature of relay 512, right contact and armature of relay 510, lower contact of sequence switch spring 524 to ground through left contact and armature of relay 506. The operation of relay 511 opens the holding circuit for relay 509 causing its release. The operation of relay 511 also opens the circuit through which the premature trirp test is being applied to ringing relay 314.

One premature trip test has now been completed. This is the first of three prematme trip tests that are made during the automatic progression of the testing device, Fig. 5. The advantage oti'making three premature trip tests is in the probability that each one otE these tests will start at a different point in the alternating current wave and thus in one or more of these tests the alternating current is connected through the winding of relay 314 when the current wave is at its peak value. In this manner the maximum surge of current is sent through the winding of relay 314 upon "the application of the premature trip test.

It will be remembered that during the first premature trip test, relay 506 operated twice under the control of interrupter 551 

